Central Heating Problem

[woodman2]

#-o Can anyone suggest what is wrong?

I have a 'normal' oil fired central heating system. The boiler is working (but not running as often as normal?) and the central heating pump, situated in the airing cupboard above the boiler, appears to be working ok.
However I am NOT getting hot water from the water cylinder and the central heating is working at a low level of heat upstairs but virtually nothing downstairs. #-o


In anticipation!!!
Woodman2

 

[Doug B]

Check your header tank (usually the smallest one in the roof) has water in it & that the ball valve hasn`t stuck in the off position


Edit

If you have a speed control on your pump increase it to maximum after checking the header tank, some times pumps can sound like the are working but not enough to circulate the water around the down stairs circuit

 

[pip1954]

or does it switch from hot water to heating when you turn on stats in room or on tank if it does not might be motorized valve might have motor gone .
if you turn both of then turn one at a time the valve will switch from hot water to heating or from heating to water.
pip

 

[Doug B]

or does it switch from hot water to heating when you turn on stats in room or on tank if it does not might be motorized valve might have motor gone .
if you turn both of then turn one at a time the valve will switch from hot water to heating or from heating to water.
pip

Not impossible but usually if you loose hot water & heating downstairs its not the motorised valve (s) as in a 3 way valve priority is to hot water & in an S plan it`s very unusual for both valves to go down together. Much more likely to be the pump if the system is full of water.

Also you need to check any manual air vents have been bled.

 

[sparkymarky]

Probably the pump.

Take the screw out from the middle of the circulating pump this will vent it of air + you can check to see if the motor is spinning. if the motor is spinning it may be a snapped shaft on the circulator between the motor and the impeller (it's rare but i have had it a couple of times).

Is the system pressurised or does it have a header tank in the loft?

If you turn off the isolation valves either side of the pump and then take the four 4mm hex bolts out the pump the motor unit will come away without disturbing the pipework this will enable you to check the condition of the pump impeller, if a grundfoss pump you can replace the pump with out replacing the pump body providing the body is in a clean and tidy condition.

Cheers

 

[Lons]

If it's a 3 way motorised zone valve, there's often a small spring loaded leverwhich can be pushed sideways and clipped into a notch. this overides and opens the valve so you can check that water is being pumped through both to h/w and heating. It's usually the motor which goes and these can be obtained seperately for most makes of valve and replaced without disturbing the plumbing. 4 screw fixing. There are a few which are all one piece however.

If it's the pump, you can often start it if seized by tapping GENTLY with a hard faced hammer. Don't belt it 'cos the casing can be cracked. #-o

Bob

 

[woodman2]

#-o Hi Guys - thanks for all your contributions to cure my heating/water problems. A local plumber replaced the motor to the 3 way zone valve. Still no joy!

I then noticed that the bottom of the door to the boiler room had began to rub on the wooden floor. This brought back memories of some 7-8 years ago when the heat exchanger fractured and water leaked out slowly over a period of time. With the front cover of the boiler removed it was obvious that it had fractured again and the dampness had caused the floor to lift slightly and to for the door to rub. I remember to heating engineer saying at the time that the heat exchangers do not last for ever!!!

Engineer looking to see if a replacement heat exchanger is still avaiable for the boiler which is 17/18 years old. An expensive time ahead methinks #-o

Woodman2

 

[Lons]

#-o Hi Guys - thanks for all your contributions to cure my heating/water problems. A local plumber replaced the motor to the 3 way zone valve. Still no joy!

I then noticed that the bottom of the door to the boiler room had began to rub on the wooden floor. This brought back memories of some 7-8 years ago when the heat exchanger fractured and water leaked out slowly over a period of time. With the front cover of the boiler removed it was obvious that it had fractured again and the dampness had caused the floor to lift slightly and to for the door to rub. I remember to heating engineer saying at the time that the heat exchangers do not last for ever!!!

Engineer looking to see if a replacement heat exchanger is still avaiable for the boiler which is 17/18 years old. An expensive time ahead methinks #-o

Woodman2

OUCH :shock:

I've had oil central heating for nearly 30 years and last boiler was 20yrs plus and never had a heat exchanger go on me. Guess I've been lucky.

I'm surprised that it looks as if your plumber might have replaced the synchronous motor needlessly. It's one of the first things to check but very easy to test. Basic stuff so he can't know much about heating systems :roll:

Bob

 

[RogerS]

As you say 'Ouch'. My old oil boiler was also built like a tank. A very basic design as well in that there really wasn't any heat exchanger per se that could be exchanged. I always associate problems with heat exchangers with condensing boilers and their narrow water pathways.

Still look on the bright side....if you do have to get a new boiler you can stick it outside and if you have long hot water runs lots of opportunity for redesign and improvement.

For very good advice re boiler selection go to AskTheTrades...also good advice on which ones NOT to buy!

 

[Tinbasher]

Check out if you can get a grant for a new more efficient boiler.

 

[Doug B]

I don`t see why a leaking heat exchanger on a boiler that you say is firing would cause the hot water & heating not to work, presuming that the leak on the exchanger is just a slight one & if it wasn`t I'm sure you`d see water else where.

If you have a header tank is the ballvalve running ?

If it`s a pressurized system are you loosing pressure?

Either of these things will tell you if you have a leak.

If your system is full of water & the boiler is firing then there is another reason for your lack of hot water & heating.

 

[Lons]

What Doug said!

Heating is not difficult to analyse.

1. Is the boiler firing and does it keep running - if not then check the oil pump which is a common fault, the filters and the jet as well as visually looking to see there is a constant sperk. Any of these will cause a lockout if faulty.
2. If yes and there is no lockout (though boiler may stop running as it will reach temperature) then the most likely is the pump. If you put your hand on it you will feel it is running and the feed pipe should be warm. Next is the zone valve which can usually be manually over ridden to test.

All this assuming of course that your controller and thermostats are functional.

Additional as said is that the water pressure on a combi system must be checked and re-filled if low after finding the cause of the leak.

Bob

 

[Pond]

#-o Hi Guys - thanks for all your contributions to cure my heating/water problems. A local plumber replaced the motor to the 3 way zone valve. Still no joy!

I then noticed that the bottom of the door to the boiler room had began to rub on the wooden floor. This brought back memories of some 7-8 years ago when the heat exchanger fractured and water leaked out slowly over a period of time. With the front cover of the boiler removed it was obvious that it had fractured again and the dampness had caused the floor to lift slightly and to for the door to rub. I remember to heating engineer saying at the time that the heat exchangers do not last for ever!!!

Engineer looking to see if a replacement heat exchanger is still avaiable for the boiler which is 17/18 years old. An expensive time ahead methinks #-o

Woodman2

You say boiler room, is it not part of the house, ie unheated? If so, the heat exchanger could have blown from thermal shock if it is cold in there at night. Unusual, though.

 

[Pond]

I don`t see why a leaking heat exchanger on a boiler that you say is firing would cause the hot water & heating not to work, presuming that the leak on the exchanger is just a slight one & if it wasn`t I'm sure you`d see water else where.

If you have a header tank is the ballvalve running ?

If it`s a pressurized system are you loosing pressure?

Either of these things will tell you if you have a leak.

If your system is full of water & the boiler is firing then there is another reason for your lack of hot water & heating.

My guess is an airlock, most likely near the pump! This could have been caused by air being drawn into the system where the weep is!

I had a similar problem on friday night. Pump was noisy, upstairs rads hot, downstairs cold. Boiler was cycling on stat. I thought pump was knacked. Bled the pump first, then the upstairs rads, this sorted it. I also turned the boiler stat down a bit, from 85c to 75c as I think the sludge in the system has been making co2 or o2 causing gas build up at higher temps..